/Engine/Plugins/Runtime/MassEntity/Source/MassEntity/Public/MassProcessingPhaseManager.h
Stores InEntityManager as the entity manager. It also kicks off phase ticking if the given InEntityManager is tied to aUWorld.
void Start ( const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FMassEntityManager](API\Plugins\MassEntity\FMassEntityManager) > & InEntityManager )